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title: "A horse is attached to a cart by a taut horizontal harness on a flat, level road. When the horse begins walking, both the horse and the cart accelerate forward together. Which of the following correctly explains why the cart accelerates forward despite the harness exerting equal and opposite forces on the horse and the cart?"
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url: "https://nerd-notes.com/ubq/120544/"
date_modified: "2026-08-23T04:41:24+00:00"
---

# A horse is attached to a cart by a taut horizontal harness on a flat, level road. When the horse begins walking, both the horse and the cart accelerate forward together. Which of the following correctly explains why the cart accelerates forward despite the harness exerting equal and opposite forces on the horse and the cart?

A horse is attached to a cart by a taut horizontal harness on a flat, level road. When the horse begins walking, both the horse and the cart accelerate forward together. Which of the following correctly explains why the cart accelerates forward despite the harness exerting equal and opposite forces on the horse and the cart?

- **A.** The forward force exerted by the harness on the cart exceeds the backward force exerted by the cart on the harness while the system is accelerating, with the forces only becoming equal in magnitude once a constant speed is reached.
- **B.** The greater mass and muscular effort of the horse allow its forward pull to overwhelm the inertia of the cart, preventing the reaction force from resisting the forward motion.
- **C.** The action-reaction pair of forces between the horse and the cart cancels out within the system, allowing the internal muscular force generated by the horse to accelerate both objects forward.
- **D.** The acceleration of the cart depends only on the horizontal forces acting directly on the cart itself; the forward pull from the harness exceeds the backward resistive forces on the cart, while the reaction force acts on the horse.

*The answer key and step-by-step explanation are available to logged-in users at https://nerd-notes.com/ubq/120544/*